Here's the official word from TIntHaus. So if in the rare event the sunroof / rear window were to crack, neither they nor Tesla would warrant it. However in saying so they have done thousands of Tesla's and not one was damaged over the years, and they still offer lifetime warranty the tint itself.
"For the rear screen we only use the Carbon based film which is not the XR Black ceramic. the Carbon film reflects minimal heat but does not absorb heat like a ceramic film does.
Whilst it is not as effective as the XR black ceramic at reducing heat is still cuts total solar energy by over 40% and is the only option which is safe to use on the rear screen.
The film we use will not adversely affect the radio transmission (as mentioned in my initial email), nor will it impact the demister lines in the back window.
Again, that’s correct we will not cover any cracking under warranty due to the tint fitment (nor will Tesla)
We will still however, provide a lifetime warranty on the rear screen against bubbling, peeling, lifting and discolouration."